Azure VM NGINX Plus + Web App leads to 404 - asp.net-mvc

Question

I'm working on NGINX Plus setup as a reverse proxy for traffic management and routing on my Azure Cloud Solution.
I'm just getting started and everything works independently, but when I try to use the proxy_pass to route web traffic to a .NET Web App that rests in the cloud, I get 404 errors.
I've tried with an app I've had deployed for a while(a .NET MVC Web App) and also a node express app that is nothing more than the basic offering as a test:
http://rpsexpressnodetest.azurewebsites.net/
Each of these runs as expected when I go the directly to them, but then when I enable the pass thru I get a 404 error.
I'm using the following config file for nginx:
user nginx;
worker_processes auto;
error_log /var/log/nginx/error.log notice;
pid /var/run/nginx.pid;
events {
worker_connections 1024;
}
http {
upstream web_rps{
server rpsexpressnodetest.azurewebsites.net;
}
# ssl_certificate /etc/nginx/ssl/server.crt;
# ssl_certificate_key /etc/nginx/ssl/server.key;
# drop requests with no Host header
# server{
# listen 80 default_server;
# server_name "";
# return 444;
# }
server{
listen *:80;
# listen *:443 ssl;
root /usr/share/nginx/html;
location / {
proxy_pass http://web_rps;
}
}
include /etc/nginx/mime.types;
default_type application/octet-stream;
log_format main '$remote_addr - $remote_user [$time_local] "$request" '
'$status $body_bytes_sent "$http_referer" '
'"$http_user_agent" "$http_x_forwarded_for"';
access_log /var/log/nginx/access.log main;
sendfile on;
#tcp_nopush on;
keepalive_timeout 65;
#gzip on;
include /etc/nginx/conf.d/*.conf;
}
In any case, if I navigate to http://rpsnginx.cloudapp.net/ (my nginx vm), I always get a 404 web app not found...
Error 404 - Web app not found.
The web app you have attempted to reach is not available in this
Microsoft Azure App Service region. This could be due to one of
several reasons:
The web app owner has registered a custom domain to point to the Microsoft Azure App Service, but has not yet configured Azure to
recognize it. Click here to read more.
The web app owner has moved the web app to a different region, but the DNS cache is still directing to the old IP Address that was used
in the previous region. Click here to read more.
If I remove the pass through proxy I get the standard "Welcome to NGINX" index.html file, so the NGINX seems to work just fine too...
I sincerely hope my new(b)ness is causing the issue.
Any assistance would be a great help!

Answer 1

First off, big props to NGINX Support for getting back to me as quickly as I could transpose this post from an email I sent them...
More importantly, here is the answer provided by them that worked!
My guess that this is this the source of the problem.
Try adding following directive to "location /" block:
proxy_set_header Host rpsexpressnodetest.azurewebsites.net;
Worked like a champ!